POS1104 PHYSIOLOGIC ADAPTIVE CHANGE OF THE PATELLAR AND ACHILLES TENDONS: SENSITIVITY TO CHANGE DETECTED BY COMPUTER ANALYSIS OF SEQUENTIAL STATIC IMAGES
Authors: C. Guillén-Astete, Á. Andreu-Suárez, M. Tortosa-Cabañas, C. Pijoan Moratalla, P. Barrio Rufino, E. Muñoz Rodriguez, J. Mollá Cuadrillero
Journal: Annals of the Rheumatic Diseases (2022)

Background Sensitivity to change is the ability of a tool to detect changes in the measurement of a variable when this measurement is made on the same target over time. In the follow-up of patients with immune-mediated diseases, it is required that the instruments used to evaluate changes over time demonstrate enough precision. However, ultrasound studies stratify the results of the evaluations in ordinal degrees of intensity of findings dependent on the evaluator’s opinion. Computer analysis of static images has recently been introduced in the study of patients with rheumatic diseases. Nonetheless, its application in musculoskeletal ultrasound is still very limited. Objectives -To determine if this type of image analysis is sensitive to structural adaptive change of the patellar and Achilles tendons in healthy subjects. Methods We recruited young volunteers with a declared sedentary habit and with a normal BMI. They carried out a supervised physical exercise routine for 6 months. Two ultrasound measurements of the patellar and the Achilles long axis were performed. Also, two elastographies of the same tendons and two anthropometric measurements of the thigh and calf were made at the beginning and end of the training period. To demonstrate sensitivity to change, a correlation was made between the ultrasound, elastrographic and anthropometric morphological changes, and the result of the computer analysis of the image in terms of gray scale mean and mode. Results 19 volunteers were evaluated (mean age 24 ±2 years, 12 women). After the exercise routine, we found statistically significant differences between calf perimeter (mean -3,70 ±1,803; p .000), Achilles elastography (-,347 ±,294; p .000), Achilles and patellar MGI (4,229 ±4,849; p .001 and 2,331 ±3,115; p,004). Regarding the non-normal distributed variables, we met statistically significant differences between patellar elastography (average range 11,45, sum of the ranks 126,00; Z -2,343; p,019), Achilles and patellar grey intensity modes (average 12,92, sum 168,00; Z -2,938; p,003 and average 11,77, sum 176,50; Z -3,28; p,001). The correlations study is shown in Table 1. Table 1. Results of the Pearson correlation tests of changes experienced over time. Variables of change (Final-Baseline) Achilles tendon elasticity change Patellar tendon elasticity change Achilles mean grey intensity changes Patellar mean grey intensity changes Achilles mode grey intensity changes Patellar mode grey intensity changes Calf circumference change Pearson correlation ,050 ,470 * ,094 ,530 * ,935 ** ,029 Sig. (bilateral) ,840 ,042 ,701 ,020 ,000 ,907 Thigh circumference change Pearson correlation ,014 -,069 ,120 -,160 ,022 ,904 ** Sig. (bilateral) ,956 ,780 ,624 ,514 ,928 ,000 Body Fat % Change Pearson correlation -,237 ,098 -,033 ,119 -,091 ,011 Sig. (bilateral) ,330 ,689 ,893 ,626 ,712 ,963 Achilles tendon elasticity change Pearson correlation 1 ,221 ,779 ** ,090 ,147 -,032 Sig. (bilateral) ,362 ,000 ,715 ,548 ,896 Patellar tendon elasticity change Pearson correlation ,221 1 ,353 ,899 ** ,416 -,154 Sig. (bilateral) ,362 ,139 ,000 ,076 ,529 Figure 1. Before (upper) and after (lower) evaluation. Conclusion Computer analysis of static images of the Achilles and patellar tendons is sensitive to the change induced by exercise in young and healthy subjects. The mean gray intensity correlates better with elastography. This shows that the predominance of the fibrillar pattern induced by exercise produces a higher speed of sound conduction. The gray intensity mode correlates better with the anthropometric changes experienced by the subjects. The concentration of shades in white extremes translates into greater anthropometric changes. This demonstrates that the stiffness or elasticity of a tendon correlates with the global distribution of gray. The response to mechanical stimuli correlates with the concentration of more intense white tones that are not necessarily scattered (endophytes or pre-enthesophytes). Disclosure of Interests Carlos Guillén-Astete Speakers bureau: Novartis, Janssen, Abbvie, Grunenthal, UCB, Gebro, Paid instructor for: Roche, Novartis, Janssen, Esteve, Menarini, Consultant of: Janssen, Novartis, Roche, Grant/research support from: Pfizer, Grunenthal, Gebro, Novartis, África Andreu-Suárez: None declared, Marina Tortosa-Cabañas: None declared, Cristina Pijoan Moratalla: None declared, Paula Barrio Rufino: None declared, Esther Muñoz Rodriguez: None declared, Jorge Mollá Cuadrillero: None declared